本論文中我們使用超快光激發-兆赫波探測(Optical-pump THz-probe)技術觀察化學氣相沉積法成長的錯位雙層石墨烯其超快載子動力學，並藉由液態閘極給予石墨烯偏壓，使其費米能階改變，觀察不同費米能階下光載子的弛豫行為。
在最早對磊晶成長的石墨烯進行研究，觀察光激發後穿透率變化為負值即光電導率變化為正值，為似半導體行為，而直到2013~2014年才有對化學氣相沉積法成長的單層石墨烯進行研究，並出現兩種不同的看法一是觀察光激發後穿透率變化為在從遠離接近至迪拉克點出現穿透率變化從正值變負值，二是光激發後穿透率變化恆為正值，恆為似金屬行為，但是在接近迪拉克點時訊號接近於零，而本文中在對化學氣相沉積法成長的錯位雙層石墨烯進行研究後，觀察到與第二種看法的單層石墨烯有相似的結果與趨勢，其原因是因為錯位雙層石墨烯的層與層之間雖然是凡德瓦力，但是依然可以傳導電子，而唯一可能會讓弛豫行為產生差別的是，經由拉曼光譜所得知，錯位雙層石墨烯的聲子色散模式會有些改變，但是改變過小，使得最終對光載子的弛豫行為影響不明顯，因此最後我們使用分析單層石墨烯的方式，解釋錯位雙層石墨烯裡光載子的弛豫現象。

In this thesis, we use optical-pump THz-probe spectroscopy to measure the ultrafast relaxation dynamics of quasi-particle in the misoriented bilayer graphene, which was fabricated by chemical vapor deposition (CVD), and then we use liquid gate to change the Fermi level of the sample for observing carrier relaxation dynamic. In early, the research about the relaxation dynamics on graphene which grown on SiC substrate was published, and it showed the negative pump induced differential transmission (PIDT), that is, a transient positive conductivity after photoexcitation. In 2013-2014, there were the different results on CVD monolayer graphene which showed the positive PIDT, and there are two kind of opinions when the Fermi level near the Dirac point. First showed the PIDT will change sign from positive to negative when near the Dirac point. Second showed the PIDT will always positive in all Fermi level and the signal will vanish when near the Dirac point, finally, the behavior of misoriented bilayer graphene is quasi-similar with the second one. Our sample differs from monolayer graphene. Electrons can transmit between two layers, and misoriented bilayer graphene have different optical phonon dispersion relation by Raman spectroscopy. However, this different is too small to have a significant impact on the carrier relaxation dynamic. The feature of response is similar to that of monolayer, therefore, we explain our experiment results by using the analysis method in monolayer graphene.

摘要 i
Abstract ii
誌謝 iii
目錄 iv
圖目錄 vii
表目錄 xi
第一章 導論 1
1.1二維材料:石墨烯的基本特性 1
1.2石墨烯發展歷史 1
1.3超快光激發-兆赫波探測(Optical-pump THz-probe)技術 3
1.4光載子在石墨烯的弛豫行為:文獻回顧 4
1.4.1 似半導體的石墨烯弛豫行為 4
1.4.2 似金屬的石墨烯弛豫行為 6
1.4.3 遠離或接近迪拉克點(Dirac point)時的石墨烯弛豫行為 8
1.5研究動機 11
第二章 石墨烯基本理論 12
2.1晶格結構 12
2.2電子能帶結構 13
2.3聲子色散特性 14
2.4石墨烯內主要色散機制 15
第三章 實驗樣品製備 17
3.1石墨烯製備簡介 17
3.1.1機械剝離法 18
3.1.2化學剝離法 18
3.1.3磊晶成長法 19
3.1.4化學氣相沉積法 19
3.2石墨烯製備 20
3.2.1銅箔事前處理 20
3.2.2化學氣相沉積法 20
3.2.3石墨烯轉移 22
3.3金屬電極與電路板製作 24
3.4液態閘極(Liquid gate)製作與使用 26
第四章 儀器原理與介紹 28
4.1拉曼光譜術(Raman spectroscopy) 28
4.1.1拉曼光譜儀原理 28
4.1.2石墨烯的拉曼分析 30
4.2時域解析頻譜系統 33
4.2.1雷射系統 33
4.2.2光激發兆赫探測時域解析頻譜系統架設 35
第五章 實驗結果分析與比較 37
5.1液態閘極對錯位雙層石墨烯改變費米能階之電阻結果 37
5.2單層石墨烯與錯位雙層石墨烯的拉曼光譜比較結果 38
5.2.1 2D(G’) peak的振幅寬度比 38
5.2.2 2D(G’) peak的振幅位置比 38
5.3 兆赫波量測時域解析結果 41
5.3.1 空氣與氮氣下兆赫波量測結果 41
5.3.2 石英基板與樣品下兆赫波量測結果 42
5.4 超快光激發-兆赫波系統穿透率量測結果 44
5.4.1改變激發光能量的穿透率量測結果 46
5.4.2改變錯位雙層石墨烯費米能階的穿透率量測結果 49
第六章 結論與展望 55
6.1結論 55
6.2展望 57
參考文獻 58
附錄-雷射操作手冊 62

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